'79 DR-103 Presence and Loudness

[ckaydrag]

Hi everybody!

My 1979 Hiwatt DR-103's Presence control operates weird. It doesn't change the sound until about 14 o'clock (the sound isn't dark before 14 o'clock, it's usable). After that it adds pretty much highs (the leap is significant). I measured the pot - it's 120kOhm, it begins to affect the sound when is about 20k and less (or 100k and more - not sure which way it works ). The pot seems to be linear - maybe it should be log etc to provide better sweep or caps are too big/small? Here's the pic of the Presence pot (resistor connected to center lug is 470R which i found is as it should be and anyway is too small comparing to 100k to affect the pot's work):

IMG_1233b.jpg (147.99 KiB) Viewed 1604 times

Also I'm interested how loud should be the DR103, especially comparing to modern amps? I mostly set preamp gain on 12 o'clock or something in this range to get the pretty clean sound. The amp is loud at max master volume but it seemed to me it's quiter than clean channel on the Engl Fireball (60 watt) head and even 30 watt local made tube combo (same thing on Peavey 5150 and Krank Revolution 1, but they're 120 and 100 watts so it's not that suspicious). I know watts can be measured differently and can't be considered as the absolute amount of loudness but just want some comparison.

[Dr.Bre]

Hi !!

Try to crank the vol up to 4 o'clock then you will s hear a loud hiwatt

[OldSchoolDave]

Not sure who "spuzzed" all over your components, but that was completely unnecessary .

Your description of the Presence control performance seems normal to me. The Hiwatt Presence is slightly better than an on/off switch, but not much.

As to volume, are you comparing apples-to-apples? Same cabinet being powered? Tubes have a lot to do with SPL. Make sure yours are up to par. I typically set my preamp volumes closer to the 2:00 o'clock range but, again, it depends on the tubes. Are you jumping channels?

Dave

[mhuss]

The Presence control in a Hiwatt is odd compared to the normal Bassman/Marshall NFB one. It sweeps between a 'HF cut' cap across the signal (counter-clockwise) and a normal NFB HF boost (clockwise). They use a linear pot to try to balance these two opposites, although, as you noted, the median is a bit clockwise of center. A log pot would be much worse.

The resistor to the center lug is just for isolation, it does nothing to affect the response.

Hiwatt used a 220k linear pot in the MV position (I think for economic purposes, since the 220k Treble needed to be linear), so you have to turn the Master up a lot higher then other amps to get to the same volume. I usually *start* at noon and turn up from there.

--mark

[ckaydrag]

Thank you for the responses!

Try to crank the vol up to 4 o'clock then you will s hear a loud hiwatt

Do you mean the master volume? I cranked it all the way up - yes it's loud Maybe I should go from the other side - how loud should be my DR-103 with the preamp gain at half or close to that. I mean how much more quite will it be when set on really clean sound comparing to itself with cranked preamp gain? Right now I moved it to my appartment so just can't crank it to find out (my neighbours will kill me )

Not sure who "spuzzed" all over your components, but that was completely unnecessary .
Your description of the Presence control performance seems normal to me. The Hiwatt Presence is slightly better than an on/off switch, but not much.

That's great to hear. Actually it doesn't make any serious trouble - just need to be more accurate than usual when setting up, the sound range it provides is ok for me.
About the goo - not sure who did this but it doesn't bother me at all and I prefer to not touch things which work. However maybe someday I'll take this goo off to make not only sound incredible but look too

As to volume, are you comparing apples-to-apples? Same cabinet being powered? Tubes have a lot to do with SPL. Make sure yours are up to par. I typically set my preamp volumes closer to the 2:00 o'clock range but, again, it depends on the tubes. Are you jumping channels?

Not 100% but pretty much - I used the same cab, the power tubes were Groove Tubes too in the Engl Fireball, though I'm not sure about the Peavey.
If I understand correct - there's only one channel since it's 2-input model. I use mostly the Normal input (Bright gives too much highs when using with high gain distortion pedals). Though I plan to try mixing channels by splitting the signal in two with active splitter and sending it to both inputs at the same time

[OldSchoolDave]

Though I plan to try mixing channels by splitting the signal in two with active splitter and sending it to both inputs at the same time

A simple "Y" cord will work fine. That's what I use on my 1980 SA112.

Dave

[ckaydrag]

A simple "Y" cord will work fine. That's what I use on my 1980 SA112.

I thought about it but I don't have one right now though have a Boss LS-2 pedal. Also my guess is that Y cord will just split my signal and feed each input with half of it while with the LS-2 I will be able to feed the amp in any proportion (for example 66% to the Normal input and 33% to the Bright - I think it will differ from just setting preamp gain knobs in the same proportions). Also it will be interesting to feed both inputs with for example 100% of signal and see if it will drive or something. Should be fun